Improvement in proof-staves for millstones



UNITED ST TE PATENT OFFICE.

JONATHAN MILLS, 0F MILWAUKEE, WISCONSIN, ASSIGNOR 0E TWO-THIRDS HIS RIGHT T0 EDWARD P. ALLIS & 00., OF SAME PLACE.

IMPROVEMENT m PROOF-'STAVES FOR MILLSTONVES.

Specification forming part of Letters Patent No. 177,537, dated May 16, 1876; application filed A April 15,1876.

To all whom it may concern:

Be it known that I, JONATHAN MILLS, of Milwaukee, in the county of Milwaukee, and State of Wisconsin, have invented certain Improvements in Proof, Staves for ,Millstones,

of which the following is a specification:

My invention consists in a straight square bar having a hole through its center from end to end, and in casting this bar on end or in an upright position. I

Theobject of my invention is to provide a cheap staff which will not have its accuracy efiected by changes in the temperature; and this end I attainby making the stafl'of metal of a square form in cross-section, providing it with a round central hole from end to end,

and planing off all four of its outer faces, thus breaking the surface all over and admitting the circulation of air through; the interior as well as around the exterior, the result of whichis that the stafl' expands and contracts equally in all directions, and remains perfectly true and straight under all circumstances.

In practice I find that the best results are attained by making the staff of cast-iron and drilling it out through the center. I also find that by casting the stafi' on end, or in an upright position, it is rendered .more perfect than otherwise, and less liable to become untrue.

' By casting the stafl on end in .an upright position, I render each transverse stratum of uniform density and texture from each side of thestafi' to the opposite side, so that upon severing the stafi' transversely at any point the metal will be found perfectly homogeneous from side to side, wherebythe opposite sides are caused to expand and contract precisely alike, and the staff thereby kept perfectly true and straight, which would not be the case were the staff cast in a horizontal position, for

the reason that the upper side would then be lighter than the lower, in consequence of which the opposite sides would expand and contract unequally and render the staff untrue.

Figure 1 represents a perspective View of the staff; Fig. 2, a longitudinal c entral section of the same; Fig. 3, an end view of the same.

its center; and b, the flat planed faces.

It is obvious that the sectional form of the stafi may be changed, but the square form ispreferred.

What I claim as my invention is- 1. The square metal stafi A, provided with the central hole I), and the planed faces a, as Shown.

2. A metal proof-staff, made in one piece, of a polygonal cross-section with a hole through its center, substantially as shown and described.

3. The herein-described method or process of forming cast-metal 'proof-staffs-that is to say, casting them on end in an upright position, as and for the purposes described.

' JONATHAN MILLS.

Witnesses:

A W. H.-WATSON, WM. W. ALLIS.

A representsthe'staff; a, the hole through 

